U.S. patent application number 14/836346 was filed with the patent office on 2016-08-04 for tire with rubber tread of intermedial and lateral zones.
The applicant listed for this patent is The Goodyear Tire & Rubber Company. Invention is credited to Roberto Cerrato Meza, Austin Gale Young, Junling Zhao.
Application Number | 20160221395 14/836346 |
Document ID | / |
Family ID | 54062619 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160221395 |
Kind Code |
A1 |
Meza; Roberto Cerrato ; et
al. |
August 4, 2016 |
TIRE WITH RUBBER TREAD OF INTERMEDIAL AND LATERAL ZONES
Abstract
The invention relates to a tire having a rubber tread of a
circumferentially zoned tread. The tread zones are comprised of
three circumferential load bearing zones, with each zone containing
a portion of the running surface of the tread, comprised of an
intermedial rubber zone positioned between and extending beneath
two stratified lateral tread rubber zones. The tread configuration
contains an underlying carbon black-rich base rubber layer. The
lateral tread rubber zones are therefore spaced apart from each
other with the intermedial tread zone therebetween and also spaced
apart from the tread base rubber layer with the intermedial tread
zone therebetween. The intermedial and stratified lateral zones are
comprised of rubber compositions having differentiated rebound
physical properties.
Inventors: |
Meza; Roberto Cerrato;
(North Canton, OH) ; Zhao; Junling; (Hudson,
OH) ; Young; Austin Gale; (Wadsworth, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Goodyear Tire & Rubber Company |
Akron |
OH |
US |
|
|
Family ID: |
54062619 |
Appl. No.: |
14/836346 |
Filed: |
August 26, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14609540 |
Jan 30, 2015 |
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14836346 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 1/0016 20130101;
B60C 2011/0016 20130101; B60C 11/0041 20130101; B60C 19/082
20130101; B60C 11/0311 20130101; B60C 2001/0083 20130101; B60C
11/0008 20130101; B60C 11/0058 20130101; B60C 2011/0025 20130101;
B60C 11/0306 20130101 |
International
Class: |
B60C 11/00 20060101
B60C011/00; B60C 1/00 20060101 B60C001/00; B60C 11/03 20060101
B60C011/03 |
Claims
1. A tire having a circumferential rubber tread composed of a
cap/base configuration comprised of an outer tread cap rubber layer
with a lug and groove configuration with the outer portions of the
tread lugs providing the running surface of the tread, and a tread
base rubber layer underlying the outer tread cap rubber layer;
wherein the outer tread cap rubber layer is composed of three
circumferential load bearing zones comprised of an intermedial
tread zone rubber layer positioned between and extending beneath
two individual stratified lateral tread zone rubber layers to
thereby underlie the lateral tread zone rubber layers and overlay
the tread base rubber layer; wherein the lateral tread zone layers
are spaced apart from each other and at least partially spaced
apart from the tread base rubber layer with the intermedial tread
zone therebetween, wherein outer tread lug surfaces of the
intermedial tread zone rubber layer and the lateral tread zone
rubber layers comprise the running surface of the tread; wherein
rubber composition of the intermedial tread zone rubber layer has a
100.degree. C. hot rebound property greater than the 100.degree. C.
hot rebound property of the rubber composition of the lateral tread
rubber layers.
2. The tire of claim 1 wherein the lateral tread rubber zones are
spaced apart from each other with the intermedial tread rubber zone
therebetween and from the underlying tread base rubber layer with
the intermedial tread rubber zone extending therebetween.
3. The tire of claim 1 wherein the lateral tread rubber zones are
spaced apart from each other with the intermedial tread rubber zone
therebetween and at least 50 percent thereof spaced apart from the
underlying tread base rubber layer with the intermedial tread
rubber zone extending therebetween and with up to 50 percent of a
lateral tread zone joined to the underlying base rubber layer by an
extension of said lateral tread rubber zone, by an extension of
said tread base rubber layer or by a rubber bridge extending
between and joining said lateral rubber zone and tread base rubber
layer.
4. The tire of claim 1 wherein the rubber composition of the
lateral tread rubber layers has a tear resistance greater than tear
resistance of the intermedial tread rubber layer.
5. The tire of claim 1 wherein, for the filler reinforcement of the
rubber compositions of the intermedial tread zone, stratified
lateral tread zones and tread base rubber zone: (A) the rubber
composition of the tread base rubber zone contains about 40 to
about 60 phr of reinforcing filler comprised of rubber reinforcing
carbon back, and (B) the rubber compositions of the intermedial and
stratified lateral tread zones contain from about 40 to about 100
phr of reinforcing filler wherein: (1) the filler reinforcement for
said lateral and intermedial tread zones is comprised of rubber
reinforcing carbon black, or (2) the filler reinforcement of said
intermedial tread zone is comprised of rubber reinforcing carbon
black and the filler reinforcement for said lateral tread zones is
a combination of rubber reinforcing carbon black and precipitated
silica comprised of: (a) at least 30 phr of rubber reinforcing
carbon black, or (b) up to about 25 phr of rubber reinforcing
carbon black, or (3) the filler reinforcement of said lateral tread
zones is comprised of rubber reinforcing carbon black and the
filler reinforcement for said intermedial tread zone is a
combination of rubber reinforcing carbon black and precipitated
silica comprised of: (a) at least 30 phr of rubber reinforcing
carbon black, or (b) up to about 25 phr of rubber reinforcing
carbon black, or (4) the filler reinforcement of both of said
lateral tread zones and intermedial tread zone is comprised of a
combination of rubber reinforcing carbon black and precipitated
silica comprised of: (a) at least 30 phr of rubber reinforcing
carbon black, or (b) up to about 25 phr of rubber reinforcing
carbon black.
6. The tire of claim 5 where the filler reinforcement for said
intermedial tread zone is a combination of rubber reinforcing
carbon black and precipitated silica comprised of up to about 25
phr of rubber reinforcing carbon black, a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by at least one of: (A)
an extension of at least one of said lateral tread rubber zones to
said tread base rubber layer, or (B) an extension of said tread
base rubber layer to at least one of said lateral tread rubber
zones, or (C) an extension of said tread base rubber layer through
said intermedial tread rubber zone to a running surface of the
outer tread rubber layer, or (D) a bridge of a rubber composition
containing filler reinforcement comprised of at least 30 phr of
rubber reinforcing carbon black, wherein said bridge extends
between and is thereby joined to said tread base rubber composition
and at least one of said later tread rubber zones.
7. The tire of claim 1 wherein the rubber composition of the
lateral tread rubber layers has a tear resistance greater than tear
resistance of the intermedial tread rubber layer.
8. The tire of claim 1 wherein a silica coupling agent is provided
for said precipitated silica, where said silica coupling agent has
a moiety reactive with hydroxyl groups on said precipitated silica
and another different moiety interactive with diene-based
elastomers in said rubber composition.
9. The tire of claim 1 wherein the filler reinforcement for said
lateral and intermedial tread zones is comprised of rubber
reinforcing carbon black.
10. The tire of claim 1 wherein the filler reinforcement of said
intermedial tread zone is comprised of rubber reinforcing carbon
black and the filler reinforcement for said lateral tread zones is
a combination of rubber reinforcing carbon black and precipitated
silica comprised of at least 30 phr of rubber reinforcing carbon
black.
11. The tire of claim 1 wherein the filler reinforcement for said
intermedial tread zone is comprised of rubber reinforcing carbon
black and the filler reinforcement for said lateral tread zones is
a combination of rubber reinforcing carbon black and precipitated
silica comprised of up to about 25 phr of rubber reinforcing carbon
black.
12. The tire of claim 1 wherein the filler reinforcement of said
lateral tread zones is comprised of rubber reinforcing carbon black
and the filler reinforcement for said intermedial tread zone is a
combination of rubber reinforcing carbon black and precipitated
silica comprised of at least 30 phr of rubber reinforcing carbon
black.
13. The tire of claim 1 wherein the filler reinforcement of said
lateral tread zones is comprised of rubber reinforcing carbon black
and the filler reinforcement for said intermedial tread zone is a
combination of rubber reinforcing carbon black and precipitated
silica comprised of up to about 25 phr of rubber reinforcing carbon
black.
14. The tire of claim 13 wherein a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by: (A) an extension of
at least one of said lateral tread rubber zones to said tread base
rubber layer, or (B) an extension of said tread base rubber layer
to at least one of said lateral tread rubber zones, or (C) an
extension of said tread base rubber layer through said intermedial
tread rubber zone to a running surface of the outer tread rubber
layer, or (D) a bridge of a rubber composition containing filler
reinforcement comprised of at least 30 phr of rubber reinforcing
carbon black, wherein said bridge extends between and is thereby
joined to said tread base rubber composition and at least one of
said later tread rubber zones.
15. The tire of claim 13 wherein a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by an extension of at
least one of said lateral tread rubber zones to said tread base
rubber layer.
16. The tire of claim 13 wherein a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by an extension of said
tread base rubber layer to at least one of said lateral tread
rubber zones.
17. The tire of claim 13 wherein a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by an extension of said
tread base rubber layer through said intermedial tread rubber zone
to a running surface of the outer tread rubber layer.
18. The tire of claim 13 wherein a path of least electrical
resistance between the tread base rubber layer and running surface
of the outer tread rubber layer is provided by a bridge of a rubber
composition containing filler reinforcement comprised of at least
30 phr of rubber reinforcing carbon black, wherein said bridge
extends between and is thereby joined to said tread base rubber
composition and at least one of said lateral tread rubber
zones.
19. The tire of claim 1 wherein tread grooves are provided in both
of said intermedial tread zone and lateral tread zones.
20. The tire of claim 1 wherein the intermedial and lateral tread
zones are configured with lugs and intervening grooves with each
lateral tread zone containing at least one tread groove and wherein
the span of the running surface of the intermedial tread zone
rubber layer axially spans from about 30 to about 80 percent of the
running surface of the tread cap rubber layer and the two lateral
tread rubber zone rubber layers collectively span from about 20 to
about 70 percent of the running surface of the tread cap rubber
layer where said span of running surface of the tread includes the
running surfaces of the tread lugs and widths of the tread grooves
between the tread lugs.
Description
[0001] The invention relates to a tire having a rubber tread of a
circumferentially zoned tread. The tread zones are comprised of
three circumferential load bearing zones, with each zone containing
a portion of the running surface of the tread, comprised of an
intermedial rubber zone positioned between and extending beneath
two stratified lateral tread rubber zones. The tread configuration
contains a carbon black reinforced rubber layer underlying the
intermedial tread rubber zone. The lateral tread rubber zones are
therefore spaced apart from each other with the intermedial tread
zone therebetween and also at least partially spaced apart from the
tread base rubber layer with the intermedial tread zone
therebetween. The intermedial and stratified lateral zones are
comprised of rubber compositions having differentiated rebound
physical properties.
BACKGROUND FOR THE INVENTION
[0002] Tire treads for pneumatic tires typically have running
surfaces of a unitary rubber composition and therefore rubber
properties attributed to the tread rubber composition across the
face of the tread. The tread is usually composed of a lug and
groove configuration composed of ground-contacting lugs with
intervening grooves between the lugs.
[0003] Tires intended for heavy duty, in a sense of carrying large
loads, such as for example truck tires, are typically intended to
experience internal heat generation during the service, or
operation, of the tire and to experience considerable stress at
lateral, portion(s) of the tread, including tread grooves contained
in the tread's ground-contacting lateral tread zones due to, for
example, vehicular cornering and tire scuffing against roadside
objects including, for example, roadside curbs. When such tire
stress is excessive, a surface cracking of a surface of a groove
wall contained in a stratified lateral zone of the tread may occur
in response to the considerable stress.
[0004] The outer, ground-contacting, tread cap rubber layer is
typically comprised of a relatively low hysteretic rubber
composition to promote relatively low internal heat generation as
the tire is used in service as evidenced by relatively high rubber
rebound physical property and relatively low tan delta physical
property to, in turn, thereby promote a low rolling resistance of
the tire tread as well as extended tread shoulder groove
durability.
[0005] For this invention, it is proposed to provide the outer
tread cap rubber layer in a form of circumferential zones of
significantly different physical properties, particularly rubber
compositions of differing physical properties such as hot rebound
(100.degree. C.) values which are indicative of hysteresis of the
rubber composition and predictive of rate of internal heat
generation during use of the tire and also predictive of rolling
resistance of the tire. For this invention, such tread zones are
provided as an intermedial rubber zone to promote lower hysteresis
with resultant lower internal heat build-up across a major portion
of the breadth of the tire tread positioned between and at least
partially underlying lateral tread rubber zones.
[0006] In particular, it is proposed to provide the intermedial
rubber zone, which extends across a major portion of the underlying
tread base rubber layer, with a higher 100.degree. C. hot rebound
property, thereby a lower hysteresis property, than the overlying
stratified lateral tread rubber zones to promote a relative
maximization of reduced internal heat build-up within the tread.
The lateral tread zone rubber composition is therefore proposed to
have a relatively lower 100.degree. C. hot rebound property,
thereby a higher hysteresis. It is further desired for the lateral
tread zone rubber composition to have a greater tear resistance
property compared to the intermedial tread zone rubber,
particularly to reinforce tread grooves contained in the stratified
lateral tread zones.
[0007] Historically, tires have heretofore been proposed having an
outer surface composed of a plurality of circumferential zones of
rubber compositions to promote various properties for the tread's
running surface.
[0008] For example, see U.S. Pat. Nos. 8,662,123; 7,789,117;
7,559,348; 7,131,474 and 6,959,744; Patent Publication Nos.
2007/0017617 and 2009/0107597; and EP0718127, EP0798142 and
DE19812934.
[0009] However, it is hereby proposed to provide a tire with tread
containing a combination of circumferential intermedial and lateral
zones of rubber compositions to promote significantly
differentiated physical properties to include rebound properties to
therefore promote differentiated hysteresis properties. As
indicated, the higher rebound property (e.g. lower hysteresis
property) for the tread intermedial zone layer, as compared to the
lateral tread zone layer, is desired to promote, or maximize, a
beneficially lower internal heat build up for the tread.
[0010] In this manner then, the central portion of the tread is a
dual layered composite of an intermedial tread cap rubber zone
layer and tread base rubber layer. The lateral portions of the
tread are triple layered composites of the stratified lateral tread
rubber zones, the portion of the intermedial tread zone which at
least partially extends beneath and underlies the lateral tread
zones and the tread base rubber layer which underlies the
intermedial tread zone.
[0011] The tire tread is thereby comprised of a cooperative layered
composite of the aforesaid circumferential rubber layers.
[0012] In one embodiment, tread grooves are contained in both the
intermedial tread zone and the lateral tread zones. By providing
the lateral tread zone rubber layers with a tear resistance
property, it is intended that tear resistance of the surface of the
grooves contained in the lateral portion of the tread is
promoted.
[0013] In the description of this invention, the terms "rubber" and
"elastomer" may be used interchangeably, unless otherwise provided.
The terms "rubber composition", "compounded rubber" and "rubber
compound" may be used interchangeably to refer to "rubber which has
been blended or mixed with various ingredients and materials" and
such terms are well known to those having skill in the rubber
mixing or rubber compounding art. The terms "cure" and "vulcanize"
may be used interchangeably unless otherwise provided. The term
"phr" may be used to refer to parts of a respective material per
100 parts by weight of rubber, or elastomer.
SUMMARY AND PRACTICE OF THE INVENTION
[0014] In accordance with this invention, a tire is provided having
a circumferential rubber tread composed of a cap/base configuration
comprised of an outer tread cap rubber layer with a lug and groove
configuration with the outer portions of the tread lugs providing
the running surface of the tread, and a tread base rubber layer
underlying the outer tread cap rubber layer;
[0015] wherein the outer tread cap rubber layer is composed of
three circumferential load bearing zones comprised of an
intermedial tread zone rubber layer positioned between and
extending beneath two individual stratified lateral tread zone
rubber layers to thereby underlie the lateral tread zone rubber
layers and overlay the tread base rubber layer;
[0016] wherein the lateral tread zone layers are spaced apart from
each other and at least partially spaced apart from the tread base
rubber layer with the intermedial tread zone therebetween,
[0017] wherein outer tread lug surfaces of the intermedial tread
zone rubber layer and the lateral tread zone rubber layers comprise
the running surface of the tread;
[0018] wherein rubber composition of the intermedial tread zone
rubber layer has a 100.degree. C. hot rebound property greater than
the 100.degree. C. hot rebound property of the rubber composition
of the lateral tread rubber layers.
[0019] In one embodiment, the lateral tread rubber zones are spaced
apart from each other with the intermedial tread rubber zone
therebetween and from the underlying tread base rubber layer with
the intermedial tread rubber zone extending therebetween.
[0020] In one embodiment, the lateral tread rubber zones are spaced
apart from each other with the intermedial tread rubber zone
therebetween and at least 50, alternately at least 80, percent
thereof spaced apart from the underlying tread base rubber layer
with the intermedial tread rubber zone extending therebetween and
with up to 50, alternately up to about 20, percent of a lateral
tread zone joined to the underlying base rubber layer by an
extension of said lateral tread rubber zone, by an extension of
said tread base rubber layer or by a rubber bridge extending
between and joining said lateral rubber zone and tread base rubber
layer.
[0021] In one embodiment, the rubber composition of the lateral
tread rubber layers has a tear resistance greater than tear
resistance of the intermedial tread rubber layer.
[0022] For the filler reinforcement of the rubber compositions of
the intermedial tread zone, stratified lateral tread zones and
tread base rubber zone:
[0023] (A) the rubber composition of the tread base rubber zone
contains about 40 to about 60 phr of reinforcing filler comprised
of rubber reinforcing carbon back, and
[0024] (B) the rubber compositions of the intermedial and
stratified lateral tread zones contain from about 40 to about 100,
alternately from about 40 to about 80, phr of reinforcing filler
wherein: [0025] (1) the filler reinforcement for said lateral and
intermedial tread zones is comprised of rubber reinforcing carbon
black, or [0026] (2) the filler reinforcement of said intermedial
tread zone is comprised of rubber reinforcing carbon black and the
filler reinforcement for said lateral tread zones is a combination
of rubber reinforcing carbon black and precipitated silica
comprised of: [0027] (a) at least 30 phr of rubber reinforcing
carbon black, or [0028] (b) up to about 25 phr of rubber
reinforcing carbon black, or [0029] (3) the filler reinforcement of
said lateral tread zones is comprised of rubber reinforcing carbon
black and the filler reinforcement for said intermedial tread zone
is a combination of rubber reinforcing carbon black and
precipitated silica comprised of: [0030] (a) at least 30 phr of
rubber reinforcing carbon black, or [0031] (b) up to about 25 phr
of rubber reinforcing carbon black, or [0032] (4) the filler
reinforcement of both of said lateral tread zones and intermedial
tread zone is comprised of a combination of rubber reinforcing
carbon black and precipitated silica comprised of: [0033] (a) at
least 30 phr of rubber reinforcing carbon black, or [0034] (b) up
to about 25 phr of rubber reinforcing carbon black.
[0035] In one embodiment, where said filler reinforcement of said
lateral tread zones is comprised of rubber reinforcing carbon black
and the filler reinforcement for said intermedial tread zone is a
combination of rubber reinforcing carbon black and precipitated
silica comprised of up to about 25 phr of rubber reinforcing carbon
black, a path of least electrical resistance between the tread base
rubber layer and running surface of the outer tread rubber layer is
provided by at least one of:
[0036] (A) an extension of at least one of said lateral tread
rubber zones to said tread base rubber layer, or
[0037] (B) an extension of said tread base rubber layer to at least
one of said lateral tread rubber zones, or
[0038] (C) an extension of said tread base rubber layer through
said intermedial tread rubber zone to a running surface of the
outer tread rubber layer, or
[0039] (D) a bridge of a rubber composition containing filler
reinforcement comprised of at least 30 phr of rubber reinforcing
carbon black, wherein said bridge extends between and is thereby
joined to said tread base rubber composition and at least one of
said lateral tread rubber zones.
[0040] For the precipitated silica (an amorphous synthetic
precipitated silica), a silica coupling is provided having a moiety
(e.g. an alkoxysilane) reactive with hydroxyl groups on said
precipitated silica and another different moiety (e.g. a
polysulfide) interactive with diene-based elastomers in said rubber
composition.
[0041] In one embodiment, the value of the 100.degree. C. hot
rebound property of the intermedial tread zone rubber composition
is at least about 4 units greater than the 100.degree. C. hot
rebound property value of the stratified tread zone rubber
composition.
[0042] For example, the 100.degree. C. hot rebound value of the
intermedial tread zone rubber composition may be in a range of from
about 60 to about 80 and the 100.degree. C. hot rebound value of
the rubber composition of the lateral tread zone rubber composition
may be in a range of from about 56 to about 76 so long as the
100.degree. C. rebound values differ by at least about 4 units
(e.g. percentage units, for example, a hot rebound value of 80 for
the intermedial zone rubber composition and hot rebound value of
76, or less, for the lateral tread zone rubber composition).
[0043] In one embodiment, it is further desired for the stratified
lateral tread zone rubber composition to have a greater or equal,
preferably greater, tear resistance property than the intermedial
tread zone rubber.
[0044] The elastomers of the rubber compositions of the intermedial
tread rubber zone and lateral tread rubber zones may be the same or
different so long as the 100.degree. C. hot rebound property of the
rubber composition of the intermedial tread rubber zone is greater
than the 100.degree. C. hot rebound property of the rubber
composition of the stratified lateral rubber zones.
[0045] In one embodiment, the span of the running surface of the
intermedial tread zone rubber layer axially spans from about 30 to
about 80 percent of the running surface of the tread cap rubber
layer and the two lateral tread rubber zone rubber layers
collectively span from about 20 to about 70 percent of the running
surface of the tread cap rubber layer where said span of running
surface of the tread includes the running surfaces of the tread
lugs and widths of the tread grooves between the tread lugs.
[0046] In one embodiment, the span of the running surfaces of the
two individual lateral tread zones may be of equal widths, or at
least of substantially equal widths, or may be asymmetrical in a
sense that they are of unequal widths, namely, for example, of
widths within about 80 to about 120 percent of each other.
[0047] As indicated, the span of the running surface of the tread
cap layer includes the outer running surface of the tread lugs
(intended to be ground contacting) and the width of the included
grooves between the lugs.
[0048] In one embodiment, the Grosch abrasion rate (e.g. Grosch
high abrasion rate) of the rubber composition of the running
surfaces of the intermedial tread rubber layer and lateral tread
zone rubber layers are desirably similar. For example, in one
embodiment their Grosch abrasion rates may be within about 5 to 20
percent of each other.
[0049] In one embodiment, the tear resistance (Newtons at
95.degree. C.) of the rubber composition of the lateral tread zones
is at least 20 percent greater than the tear resistance of the
rubber composition of the intermedial tread zone.
[0050] In one embodiment, the lateral tread zones, intermedial
tread zone and underlying tread base are co-extruded together to
form an integral and unified tread composite.
[0051] In one embodiment, the rubber composition of the
intermedial, tread cap zone has a lower tan delta value at 10
percent strain (100.degree. C.) than the rubber composition of the
two lateral tread cap zones which is predictive of lower hysteresis
which is, in turn, predictive of lower internal heat buildup during
tire service and a beneficially lower rolling resistance
contribution of the intermedial tread cap rubber layer for the
tire.
[0052] Accordingly, it is an aspect of this invention to provide a
significant balance of physical properties of rubber compositions
between the intermedial tread zone and stratified lateral tread
zones in a manner of being a departure from past practice.
[0053] It is to be appreciated that one having skill in rubber
compounding for tire treads can readily provide the tread zones
with the indicated rubber composition properties with routine
experimentation and without undue experimentation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Drawings are presented as FIG. 1 (FIG. 1), FIG. 2 (FIG. 2)
and FIG. 3 (FIG. 3) to provide a further understanding of the
invention.
[0055] FIG. 1 (FIG. 1) is provided to illustrate a partial cross
sectional view of a tire with a circumferential tread of a cap/base
configuration where the outer cap rubber layer is divided into
three circumferential tread zones comprised of an intermedial and
spaced apart lateral zones. A tread base rubber layer underlies the
intermedial tread layer. A portion of the intermedial tread zone
extends in an axially outward direction from each side of the
intermedial tread zone beneath the lateral tread zones and thereby
joins and separates the lateral tread zones from each other.
[0056] FIG. 2 illustrates the tire of FIG. 1 where the tread base
rubber layer is an extension of a lateral tread rubber zone to
thereby optionally provide a path of least electrical resistance
extending between a lateral tread rubber zone and tire sidewall
rubber layer.
[0057] FIG. 3 (FIG. 3) represents the tire of FIG. 1 with a path of
least electrical resistance extending between either an intermedial
or lateral tread rubber zone and tread base rubber layer comprised
of a rubber bridge in a form of a rubber wedge.
THE DRAWINGS
[0058] In the Drawings, FIG. 1 illustrates a pneumatic tire partial
cross section (1) having a tread (2) of a cap/base configuration,
namely an outer tread cap rubber layer (3) of a lug and groove
configuration and an underlying tread base rubber layer (4). The
outer tread cap rubber layer (3) contains tread running surfaces
(not numbered) contained on the outer surfaces of the tread lugs of
the tread (2) and is composed of three circumferential tread zones,
each a part of the tread's running surface, comprised of an
intermedial tread zone rubber layer (6) between two spaced apart
individual lateral tread rubber zones (5A) and (5B) of which
portions (6A) and (6B) of the intermedial tread zone (6) extend
beneath and thereby underlie both of the lateral tread zones (5A)
and (5B) and also overlay the tread base rubber layer (4). The
outlying lateral tread zones (5A) and (5B) are thereby spaced apart
from each other. The tread base rubber layer (4) thereby underlies
the intermedial tread zone rubber layer (6) and is exclusive of the
lateral tread zones (5A) and (5B). The lateral tread zones (5A) and
(5B) are shown as being of the same width although they may be of
widths which differ from each other.
[0059] The rubber composition of one of said intermedial tread zone
(6) or lateral tread zones (5A and/or 5B) is provided as an
electrically resistive rubber composition containing a silica-rich
reinforcing filler comprised of at least 30 phr of precipitated
silica reinforcement and a maximum of 25 phr of rubber reinforcing
carbon black which therefore renders the intermedial tread rubber
composition electrically resistive relative to the lateral tread
zone rubber compositions.
[0060] The rubber compositions of the intermedial tread zone (6)
and lateral tread zones (5A) and (5B) which do not contain said
silica-rich reinforcing filler, as well as the tread base rubber
layer (4) and sidewall rubber layer (9), and bridging rubber
component (10) shown in FIG. 3, are provided as electrically
conductive rubber compositions containing a carbon black-rich
reinforcing filler comprised of at least 30 phr rubber reinforcing
carbon black which thereby renders them relatively less
electrically resistive, therefore relatively more electrically
conductive, than the aforesaid silica-rich filler containing rubber
compositions of any of the said lateral tread zones (5A and 5B) or
intermedial tread rubber zone (6).
[0061] The tread lug and groove configuration of the tread cap
rubber layer provides tread lugs with intervening grooves with
grooves (7) contained in the intermedial tread zone layer (6) and
grooves (7A) and (7B) contained in the lateral tread zone layers
(5A) and (5B) with each of the lateral tread zones thereby
containing at least one tread groove. For such purpose, it is
desired that the lateral tread zone layer rubber compositions have
a significantly greater tear resistance property than the
intermedial zone layer rubber composition to thereby aid in
protecting the tread grooves (7A) and (7B) contained in the
stratified lateral tread zone layers (5A) and (5B).
[0062] For FIG. 1, the intermedial tread zone (6) is depicted as
constituting about 45 to 60 percent of the spanned running surface
of the tire tread (2) and the two individual lateral tread zone
layers (5A) and (5B) are of a substantially equal width and
correspondingly collectively constitute about 55 to about 40
percent of the spanned running surface of the tire tread (2).
[0063] For exemplary FIG. 1, the intermedial and stratified lateral
tread zone rubber compositions may be comprised of the same or
different elastomers so long as the 100.degree. C. hot rebound
property of the intermedial zone rubber is greater than that of the
stratified lateral zone rubbers.
[0064] As indicated, the span of the running surface of the tread
cap layer includes the outer running surface of the tread lugs
(intended to be ground contacting) and the width of the included
grooves between the lugs.
[0065] For FIG. 2, a path of least electrical resistance is
provided between the lateral tread rubber zones (5A) and 5(B) to
the tread base rubber layer (4) by an extension (8) of lateral
tread rubber zones (5A) and (5B) which extends from the lateral
tread zone to and joins the tread base rubber layer (4) and
optionally also joins and overlays the tire sidewall (9).
[0066] For FIG. 3, a path of least electrical resistance is
provided between carbon black rich lateral tread rubber zones (5A)
and 5(B), and the tread base rubber layer (4), all of which are
carbon black rich in a sense of containing at least 35 phr of
rubber reinforcing carbon back, by a bridge rubber component (10)
which also contains at least 35 phr of rubber reinforcing carbon
black and which is positioned between and joins the lateral tread
rubber zones (5A) and (5B) and tread base rubber layer (4).
[0067] For FIGS. 1, 2 and 3, the tread base rubber layer (4) may,
for example, be primarily comprised of either cis 1,4-polyisoprene
rubber, preferably natural rubber, or a combination of the cis
1,4-polyisoprene rubber and a polybutadiene rubber selected from
cis 1,4-polybutadiene rubber and trans 1,4-polybutadiene rubber.
Optionally, also it may also contain up to about 20 phr (e.g. from
about 5 to about 15 phr) of at least one additional conjugated
diene based elastomer such as, for example, at least one additional
diene-based elastomer selected from at least one of
styrene/butadiene rubber, isoprene/butadiene rubber, trans
1,4-polybutadiene, low vinyl polybutadiene having vinyl content in
a range of 10 to about 40 percent, and styrene/isoprene/butadiene
rubber, preferably a styrene/butadiene copolymer rubber. In
practice, the coupling agent for the precipitated silica
reinforcement of the respective zones of the tread may be, for
example, an alkoxysilyl polysulfide such as for example, a
bis(3-trialkoxysilylalkyl) polysulfide wherein alkyl radicals for
said alkoxy groups are selected from one or more of methyl and
ethyl radicals, preferably an ethyl radical and the alkyl radical
for said silylalkyl component is selected from butyl, propyl and
amyl radicals, preferably a propyl radical and wherein said
polysulfide component contains from 2 to 8, with an average of from
2 to 2.6 or an average of from 3.5 to 4, connecting sulfur atoms in
its polysulfidic bridge, preferably an average of from 2 to 2.6
connecting sulfur atoms to the exclusion of such polysulfides
having greater than 2.6 connecting sulfur atoms.
[0068] Representative of such coupling agents are, for example,
bis(3-triethoxysilylpropyl) polysulfide having an average of from 2
to 2.6 or an average of from 3.5 to 4, connecting sulfur atoms in
its polysulfidic bridge, sometimes preferably an average of from 2
to 2.6 connecting sulfur atoms to the exclusion of a
bis(3-triethoxysilylpropyl) polysulfide containing an average of
greater than 2.6 connecting sulfur atoms in its polysulfidic
bridge.
[0069] Such coupling agent may, for example, be added directly to
the elastomer mixture or may be added as a composite of
precipitated silica and such coupling agent formed by treating a
precipitated silica therewith or by treating a colloidal silica
therewith and precipitating the resulting composite.
[0070] In practice, the synthetic amorphous silica (precipitated
silica) may be aggregates of precipitated silica, which is intended
to include precipitated aluminosilicates as a co-precipitated
silica and aluminum.
[0071] Such precipitated silica is, in general, well known to those
having skill in such art. For example, such precipitated silica may
be precipitated by controlled addition of an acid such as, for
example, hydrochloric acid or sulfuric acid, to a basic solution
(e.g. sodium hydroxide) of a silicate, for example, sodium
silicate, usually in the presence of an electrolyte, for example,
sodium sulfate. Primary, colloidal silica particles typically form
during such process which quickly coalesce to form aggregates of
such primary particles and which are then recovered as precipitates
by filtering, washing the resulting filter cake with water or an
aqueous solution, and drying the recovered precipitated silica.
Such method of preparing precipitated silica, and variations
thereof, are well known to those having skill in such art.
[0072] The precipitated silica aggregates preferably employed in
this invention are precipitated silicas such as, for example, those
obtained by the acidification of a soluble silicate, e.g., sodium
silicate and may include co-precipitated silica and a minor amount
of aluminum. The precipitated silica is therefore considered as
being an amorphous synthetic precipitated silica.
[0073] Such precipitated silicas might be characterized, for
example, by having a BET surface area, as measured using nitrogen
gas, in a range of about 40 to about 600, and more usually in a
range of about 50 to about 300, square meters per gram. The BET
method of measuring surface area is understood to be described in
the Journal of the American Chemical Society, Volume 60, Page 304
(1930).
[0074] The silica may also be typically characterized, for example,
by having a dibutylphthalate (DBP) absorption value in a range of
about 50 to about 400 cm.sup.3/100 g, and more usually about 100 to
about 300 cm.sup.3/100 g.
[0075] Various commercially available precipitated silicas may be
considered for use in this invention such as, only for example
herein, and without limitation, silicas from PPG Industries under
the Hi-Sil trademark with designations Hi-Sil 210, Hi-Sil 243,
etc.; silicas from Solvay as, for example, Zeosil 1165MP and Zeosil
165GR, silicas from J. M. Huber Corporation as, for example, Zeopol
8745 and Zeopol 8715, silicas from Evonik.
[0076] Representative examples of other silica couplers may be
organomercaptosilanes such as, for example, triethoxy
mercaptopropyl silane, trimethoxy mercaptopropyl silane, methyl
dimethoxy mercaptopropyl silane, methyl diethoxy mercaptopropyl
silane, dimethyl methoxy mercaptopropyl silane, triethoxy
mercaptoethyl silane, and tripropoxy mercaptopropyl silane. For
this invention, it is desirable for physical properties of the
sulfur cured rubber compositions of the tire tread zones to be as
presented in the following Table A.
TABLE-US-00001 TABLE A Intermedial zone rubber At least 4 units
greater than the rubber of composition rebound the lateral tread
zones value (100.degree. C.) Intermedial zone rubber At least 10
percent less than the rubber of composition Tan Delta the lateral
tread zones value (1 Hertz, 10% strain, 100.degree. C.) Lateral
zone rubber At least 20 percent greater than the rubber composition
tear of the intermedial tread zone resistance, 95.degree. C., in
Newtons
[0077] The tear resistance may be determined, for example, by ASTM
D1876-1 taken with DIN 53539 using a 5 mm wide tear width provided
by a longitudinal open space, sometimes referred to as a window,
cut or otherwise provided, in the film positioned between the two
rubber test pieces where the window provides a geometrically
defined area, namely the tear width, for portions of two rubber
test pieces to be pressed and cured together after which the force
to pull the test pieces apart is measured.
[0078] In practice, the invention the rubber compositions for the
tire tread components may be prepared in a sequential series of at
least two separate and individual preparatory internal rubber
mixing steps, or stages, in which the diene-based elastomer is
first mixed with the prescribed carbon black and/or silica in a
subsequent, separate mixing step and followed by a final mixing
step where curatives are blended at a lower temperature and for a
substantially shorter period of time.
[0079] It is conventionally required after each mixing step that
the rubber mixture is actually removed from the rubber mixer and
cooled to a temperature of less than 40.degree. C. and, for
example, in a range of about 40.degree. C. to about 20.degree. C.
and then added back to an internal rubber mixer for the next
sequential mixing step, or stage.
[0080] The forming of a tire component is contemplated to be by
conventional means such as, for example, by extrusion of rubber
composition to provide a shaped, unvulcanized rubber component such
as, for example, a tire tread. Such forming of a tire tread is well
known to those having skill in such art.
[0081] It is understood that the tire, as a manufactured article,
is prepared by shaping and sulfur curing the assembly of its
components at an elevated temperature (e.g. 140.degree. C. to
180.degree. C.) and elevated pressure in a suitable mold. Such
practice is well known to those having skill in such art.
[0082] It is readily understood by those having skill in the art
that the rubber composition would be compounded by methods
generally known in the rubber compounding art, such as mixing the
various sulfur-vulcanizable constituent rubbers with various
commonly used additive materials, as herein before discussed, such
as, for example, curing aids such as sulfur, activators, retarders
and accelerators, processing additives, such as rubber processing
oils, resins including tackifying resins, silicas, and
plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes,
antioxidants and antiozonants, peptizing agents and reinforcing
materials such as, for example, carbon black. As known to those
skilled in the art, depending on the intended use of the sulfur
vulcanizable and sulfur vulcanized material (rubbers), the
additives mentioned above are selected and commonly used in
conventional amounts.
[0083] Typical amounts of fatty acids, if used which may be
comprised of stearic acid which may also contain at least one of
palmitic and oleac acids, may comprise about 0.5 to about 3 phr.
Typical amounts of zinc oxide comprise about 1 to about 5 phr.
Typical amounts of waxes, if used, comprise about 1 to about 5 phr.
Often microcrystalline waxes are used. Typical amounts of
peptizers, if used, comprise about 0.1 to about 1 phr. Typical
peptizers may be, for example, pentachlorothiophenol and
dibenzamidodiphenyl disulfide.
[0084] The vulcanization is conducted in the presence of a sulfur
vulcanizing agent. Examples of suitable sulfur vulcanizing agents
include elemental sulfur (free sulfur) or sulfur donating
vulcanizing agents, for example, an amine disulfide, polymeric
polysulfide or sulfur olefin adducts. Preferably, the sulfur
vulcanizing agent is elemental sulfur. As known to those skilled in
the art, sulfur vulcanizing agents are used in an amount ranging
from about 0.5 to about 4 phr, or even, in some circumstances, up
to about 8 phr, with a range of from about 1.5 to about 2.5,
sometimes from about 2 to about 2.5, being preferred.
[0085] Accelerators are used to control the time and/or temperature
required for vulcanization and to improve the properties of the
vulcanizate. In one embodiment, a single accelerator system may be
used, i.e., primary accelerator. Conventionally and preferably, a
primary accelerator(s) is used in total amounts ranging from about
0.5 to about 4, preferably about 0.8 to about 2.5, phr. In another
embodiment, combinations of a primary and a secondary accelerator
might be used with the secondary accelerator being used in smaller
amounts (of about 0.05 to about 3 phr) in order to activate and to
improve the properties of the vulcanizate. Combinations of these
accelerators might be expected to produce a synergistic effect on
the final properties and are somewhat better than those produced by
use of either accelerator alone. In addition, delayed action
accelerators may be used which are not affected by normal
processing temperatures but produce a satisfactory cure at ordinary
vulcanization temperatures. Vulcanization retarders might also be
used. Suitable types of accelerators that may be used in the
present invention are amines, disulfides, guanidines, thioureas,
thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
Preferably, the primary accelerator is a sulfenamide. If a second
accelerator is used, the secondary accelerator is preferably a
guanidine, dithiocarbamate or thiuram compound.
[0086] The mixing of the rubber composition can preferably be
accomplished by the aforesaid sequential mixing process. For
example, the ingredients may be mixed in at least three stages,
namely, at least two non-productive (preparatory) stages followed
by a productive (final) mix stage. The final curatives are
typically mixed in the final stage which is conventionally called
the "productive" or "final" mix stage in which the mixing typically
occurs at a temperature, or ultimate temperature, lower than the
mix temperature(s) of the preceding non-productive mix stage(s).
The terms "non-productive" and "productive" mix stages are well
known to those having skill in the rubber mixing art.
Example I
[0087] Proposed rubber compositions were prepared for use for the
intermedial and lateral tread zone rubber layers for the tire of
this invention.
[0088] The term "CB-rich" is used to identify the reinforcing
filler in the rubber composition as being carbon black rich (a
majority of the filler is rubber reinforcing carbon black).
[0089] The term "Si-rich" is used to identify the reinforcing
filler in the rubber composition as being precipitated silica black
rich (a majority of the filler is precipitated silica).
[0090] The proposed intermedial tread zone rubber composition is
referred in this Example as rubber Samples A and B. Rubber Sample A
is referred to as being carbon black rich (CB-rich) in a sense of
its reinforcing filler being composed of about 35 phr of rubber
reinforcing carbon black and only about 15 phr of precipitated
silica. Rubber Sample B is referred to as being silica rich
(Si-rich) in a sense of its reinforcing filler being comprised of
about 50 phr of precipitated silica and only 6 phr of carbon black
contained in the silica coupling agent composite.
[0091] The proposed lateral tread zone rubber composition is
referred in this Example as rubber Samples C and D. Rubber Sample C
is referred to as being carbon black rich (CB-rich) in a sense of
its reinforcing filler being composed of about 35 phr of rubber
reinforcing carbon black and only about 15 phr of precipitated
silica. Rubber Sample D is referred to as being silica rich
(Si-rich) in a sense of its reinforcing filler comprised of about
50 phr of precipitated silica and only 6 phr of carbon black
contained in the silica coupling agent composite.
[0092] The basic rubber composition formulations are shown in Table
1 and the ingredients are expressed in terms of parts by weight per
100 parts rubber (phr) unless otherwise indicated.
[0093] The rubber composition may be prepared by mixing the
elastomers(s) without sulfur and sulfur cure accelerators in a
first non-productive mixing stage (NP-1) in an internal rubber
mixer, for example, for about 4 minutes to a temperature of, for
example, of about 160.degree. C. If desired, the rubber mixture may
then mixed in a second non-productive mixing stage (NP-2) in an
internal rubber mixer, for example, for about 4 minutes to a
temperature of, for example, about 160.degree. C. with or without
adding additional ingredients. The resulting rubber mixture may
then be mixed in a productive mixing stage (PR) in an internal
rubber mixer with sulfur and sulfur cure accelerator(s), for
example, for about 2 minutes to a temperature of, for example,
about 110.degree. C. The rubber composition may then sheeted out
and cooled to, for example, below 50.degree. C. between each of the
non-productive mixing steps and prior to the productive mixing
step. Such rubber mixing procedure is well known to those having
skill in such art.
[0094] The following Table 1 presents basic rubber formulations for
proposed intermedial tire tread zone (rubber Samples A and B) and
peripheral (lateral) tire tread zone (rubber Samples C and D)
rubber compositions for the zoned tread of this invention.
TABLE-US-00002 TABLE 1 (Intermedial and Lateral Tread Cap Zones)
Parts (phr) (Intermedial) (Lateral) A B C D CB-rich Si-rich CB-rich
Si-rich Non-productive Mix Step (NP1) Natural cis 1,4-polyisoprene
35 40 35 40 rubber (TTR20) Cis 1,4-polybutadiene rubber.sup.1 65 60
65 60 Carbon black (N205) 35 0 0 0 Carbon black (N121) 0 0 35 0
Silica, precipitated.sup.2 15 50 15 50 Silica coupling agent.sup.3
1.2 0 0 0 Composite of silica coupling 0 0 4 12 agent and carbon
black (50/50 weight ratio).sup.4 Composite of silica coupling 0 12
0 0 agent and carbon black (50/50 weight ratio).sup.5 Oil, rubber
processing.sup.6 0 5 0 0 Wax microcrystalline and 1.5 1.5 1.5 1.5
paraffin Fatty acid.sup.7 2 2 2 2 Antioxidants 3.5 4 4 3.5 Zinc
oxide 4 3 3 3 Final Mix Step (PR) Sulfur 1.5 1.8 0.9 1.2
Accelerator(s).sup.8 1.5 2.15 1.5 1.55 .sup.1Cis 1,4-polybutadiene
rubber (said organic solvent solution polymerized 1,3-butadiene
monomer in the presence of a neodymium catalyst) as either Budene
1223 .TM. from The Goodyear Tire & Rubber Company or CB25 .TM.
from the Lanxess Company, or having a Tg of about -105.degree. C.
and heterogeneity index in a range of from about 1.5/1 to about
2.2/1 .sup.2Precipitated silica as Zeosil .TM. 1165 MP .TM. from
Solvay .sup.3Silica coupling agent comprised of
bis(3-triethoxysilylpropyl) polysulfide having an average of from
about 2 to about 2.6 connecting sulfur atoms as Si266 .TM. from
Evonik .sup.4Composite of silica coupling agent and carbon black
(carrier) in a 50/50 weight ratio where said coupling agent is
comprised of bis(3-triethoxysilylpropyl) polysulfide having an
average of from about 2 to about 2.6 connecting sulfur atoms as
Si266 .TM. from Evonik .sup.5Composite of silica coupling agent and
carbon black (carrier) in a 50/50 weight ratio where said coupling
agent is comprised of bis(3-triethoxysilylpropyl) polysulfide
having an average of from about 3.4 to about 3.8 connecting sulfur
atoms as Si69 .TM. from Evonik .sup.6Rubber processing oil
.sup.7Mixture comprised of stearic, palmitic and oleic acids
.sup.8Sulfenamide with diphenyl guanidine sulfur cure
accelerators
[0095] The following Table 2 represents the uncured and cured
behavior and various physical properties of the rubber compositions
for the intermedial (rubber Sample A) and lateral (rubber Sample B)
tire tread zone rubber layers based upon the basic formulations
illustrated in Table 1.
TABLE-US-00003 TABLE 2 (Intermedial) (Lateral) A B C D Properties
CB-rich Si-rich CB-rich Si-rich RPA (Rubber Process Analyzer)
test.sup.1 Dynamic storage modulus (G'), 1.41 1.70 1.09 1.7 cured
rubber G' (1 Hertz, 10% strain, 100.degree. C.), MPa Tan delta (1
Hertz, 10% strain, 0.127 0.079 0.173 0.143 100.degree. C.)
Stress-strain, ATS.sup.27 Tensile strength (MPa) 19.8 16.5 24.6
19.8 Elongation at break (%) 464 364 560 674 300% modulus, ring,
(MPa) 11.8 13.4 11.5 7.1 Rebound 23.degree. C. 60 64 56 52
100.degree. C. 69 74 64 62 Shore A hardness, 23.degree. C. 67 65 62
67 Tear strength (tear resistance).sup.3, N 67 62 160 162 at
95.degree. C. Abrasion rate (mg/km), Grosch.sup.4 514 563 553 519
high severity (70N), 12.degree. slip angle, speed = 20 km/hr.,
distance = 250 m .sup.1RPA, rubber property analytical instrument
.sup.2Automated Test System instrument (ATS), Instron Corporation,
which incorporates a number of tests in one analytical system and
reports data from the tests such as, for example, ultimate tensile
strength, ultimate elongation, modulii and energy to break data.
.sup.3Data obtained according to a tear strength (peal adhesion),
or tear resistance test. The tear resistance may be determined by
ASTM D1876-01 taken with DIN 53539 using a 5 mm wide tear width
provided by a longitudinal open space, sometimes referred to as a
window, cut or otherwise provided, in the film positioned between
the two rubber test pieces where the window provides a
geometrically defined area, namely tear width, for portions of two
rubber test pieces to be pressed and cured together after which the
ends of the two test pieces are pulled apart at right angles
(90.degree. + 90.degree. = 180.degree. to each other) and the force
to pull the test pieces apart is measured. An Instron instrument
may be used to pull the rubber pieces apart using an Instron
instrument at 95.degree. C. with the force required being reported
as Newtons force. .sup.4The Grosch high severity abrasion rate may
be conducted on an LAT-100 Abrader and is measured in terms of
mg/km of rubber abraded away. The test rubber sample is placed at a
slip angle under constant load (Newtons) as it traverses a given
distance on a rotating abrasive disk (disk from HB Schleifmittel
GmbH). In practice, a high abrasion severity test may be run, for
example, at a load of 70 Newtons, 12.degree. slip angle, disk speed
of 20 km/hr and distance of 250 meters.
[0096] It is seen in Table 2 that the Experimental rubber Samples A
and B (rubber composition proposed for the intermedial tread zone)
and Experimental rubber Samples C and D (rubber composition
proposed for the lateral tread zones) fulfilled the beneficially
desired physical property relationships presented in Table A for
100.degree. C. hot rebound, and tear resistance (95.degree. C.)
values.
[0097] In Table 2 it is seen that the rebound value for rubber
Samples A and B (proposed intermedial tread zone rubber
composition) was greater than for the rubber Samples C and D
(proposed peripheral tread zone rubber composition) which is
indicative of beneficially lower hysteresis which in turn is
predictive of a beneficially lower rate of internal heat generation
in the intermedial tread zone rubber composition as well as
predictively beneficial reduction of rolling resistance for the
tire with a resulting predictive fuel economy for a vehicle using
such tires.
[0098] Further, in Table 2 it is seen that tear resistance for
rubber Samples C and D (proposed lateral tread zone rubber
compositions) was beneficially significantly greater than for
rubber Samples A and B (proposed intermedial tread zone rubber
composition).
[0099] Further, it is seen in Table 2 that the high severity Grosch
rates of abrasion for both rubber Samples A and B (proposed
intermedial tread zone rubber) and rubber Samples C and D (lateral
tread zone rubber) are similar, which is a desirable feature.
[0100] Further, it is seen in Table 2 that the tangent delta (tan
delta) value for rubber Samples C and D (proposed lateral tread
zone rubber) is greater than for rubber Samples A and B (proposed
intermedial tread zone rubber). Such tan delta properties, taken
with the aforesaid rebound properties, are a further indication of
lower hysteresis, lower internal heat generation during tire
service for the intermedial tread rubber zone as well as the
aforesaid predictive beneficial promotion of reduction in tire
rolling resistance for increased vehicular fuel economy.
[0101] In summary and conclusion, a tire is provided with a
configured circumferential tread zones to provide a running surface
with zones having similar rates of abrasion resistance but with
lower hysteresis in the intermedial tread zone which extends
axially outward both between and beneath the higher hysteresis
lateral tread zones for a purpose of maximizing such lower
hysteresis for the tread and with a higher tear resistance for the
lateral tread rubber zone to promote resistance to groove surface
cracking in tread groove(s) contained in the lateral tread
zones.
[0102] Such innovative tread configuration is intended to promote
lower rolling resistance for the tire tread across the width of the
tread by the extended intermedial tread zone which extends axially
outward beneath the stratified lateral tread zones and to
beneficially promote tear resistance for the outlying stratified
lateral tread zones, the combination of which is considered to be a
significant departure from past practice.
[0103] While certain representative embodiments and details have
been shown for the purpose of illustrating the invention, it will
be apparent to those skilled in this art that various changes and
modifications may be made therein without departing from the spirit
or scope of the invention.
* * * * *